Method and system for automatically maintaining an operator selected roll orientation at a distal tip of a robotic endoscope

ABSTRACT

In a robotic endoscope system, the orientation of a captured camera view at a distal tip of a robotic endoscope and displayed on a screen viewable by an operator of the endoscope is automatically maintained at a roll orientation associated with a setpoint so as not to disorient the operator as the endoscope is moved, flexed and its tip turned in different orientations. A processor generates a current commanded state of the tip from operator input and modifies it to maintain the setpoint roll orientation. To generate the modified current commanded state, the current commanded roll position and velocity are constrained to be a modified current commanded roll position and velocity that have been modified according to a roll angular adjustment indicated by a prior process period commanded state of the tip and the setpoint. The processor then commands the robotic endoscope to be driven to the modified commanded state.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. ProvisionalApplication No. 61/303,365, entitled “METHOD AND SYSTEM FORAUTOMATICALLY MAINTAINING AN OPERATOR SELECTED ROLL ORIENTATION AT ADISTAL TIP OF A ROBOTIC ENDOSCOPE” filed on Feb. 11, 2010 (AttorneyDocket No. ISRG02470PROV).

FIELD OF THE INVENTION

The present invention generally relates to robotic endoscopes and inparticular, to a method and system for automatically maintaining anoperator selected roll orientation at a distal tip of a roboticendoscope while controlling operator commanded movement of the roboticendoscope tip.

BACKGROUND OF THE INVENTION

An endoscope is a medical device that allows physicians to captureimages of and diagnose problems with internal body organs by insertingthe device either through a natural orifice or a surgeon created openingand guiding it to a target site within a patient. In some cases, it mayalso be used to perform medical procedures on the internal body organs.It may be steerable so that its distal tip is controllably oriented andpositioned for navigation purposes. An image capturing device such as astereoscopic or monoscopic camera may be provided at its distal tip sothat images captured by the camera from that perspective may be viewedon a display screen by the surgeon. To perform various medicalprocedures at the target site, surgical tools, such as those used forcutting, grasping, cauterizing, etc., may extend out of the endoscope'sdistal tip.

The endoscope may be rigid such as those used in laparoscopy or it maybe flexible so that it is capable of following the curvatures of bodylumens. It may also be rigidizable and/or robotic. A rigidizableendoscope is an endoscope that has at least one section of its flexiblebody that can be made substantially rigid by a mechanical lockingmechanism. A robotic endoscope is a flexible endoscope that has at leastone section that bends under a computer controlled servo mechanism.

Natural Orifice Transluminal Endoscopic Surgery (“NOTES”) may employ asteerable endoscope to perform surgical procedures on patients. As anexample, a flexible endoscope may be guided through one of the body'sorifices and enter the abdomen from the inside of the patient, ratherthan through a minimally invasive incision from the outside. Forexample, in “transgastric” surgery, instruments are passed through themouth and into the stomach. A gastrotomy is then performed so that theinstruments may enter the abdomen and be used by the surgeon to performa medical procedure within the abdominal cavity. Once the procedure iscompleted, the instruments are withdrawn along with any tissue removedduring the procedure, and the entry point is closed back up. Because noexternal incisions are made in the patient to accommodate entry of theendoscope, NOTES may be even less painful than surgery using minimallyinvasive incisions. Also, since it uses a natural body orifice insteadof external incisions to enter the body, it may result in reduced needsfor general anesthetics and faster recovery times.

During the operation of an endoscope, the endoscope tip may be turnedmultiple times and in different directions while moving towards, orwhile performing a medical procedure at, a target site. As aconsequence, the orientation of images captured at the distal tip of theendoscope may change and it operator may become disoriented when viewingthe captured images. If the operator accidentally moves the endoscopetip in the wrong direction as a result of such disorientation, the tipmay inadvertently perforate or otherwise damage tissue causing harm tothe patient. Even if such harm is avoided by carefully moving theendoscope tip, additional time is required to repeatedly ascertain thetrue orientation of the endoscope tip relative to the target site in thepatient. Thus, the time required to perform the procedure is lengthenedwhich adds to the cost of the surgery and increases health safetyconcerns.

U.S. Pat. No. 7,134,992 to Schara et al. (2006), which is incorporatedherein by reference, discloses a method for presenting an endoscopeimage in a gravity referenced, upright orientation by sensing a rotationof the endoscope and rotating the endoscopic image accordingly tocompensate for the sensed rotation before displaying the rotated imageon a video display device.

One problem with such an image rotation technique is that when toolsextend out of the distal end of the endoscope, they may not be orientedcorrectly from the operator's viewpoint of a captured image for the taskat hand. Also, although it may be convenient to use gravity as areference for orienting the image, it is desirable to eliminate the costand complexity of additional hardware dedicated to sensing the directionof gravity. Further, it may be useful at times to provide the operatorwith a means to select a different orientational reference.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, one object of one or more aspects of the present inventionis a method, and a system for performing the method, of automaticallymaintaining a desired roll orientation at a distal tip of a roboticendoscope while moving the robotic endoscope tip towards or at a targetsite within a patient.

Another object of one or more aspects of the present invention is amethod, and a system for performing the method, of automaticallymaintaining a desired roll orientation at a distal tip of a roboticendoscope without need for a roll angle sensor at the distal tip.

Still another object of one or more aspects of the present invention isa method, and a system for performing the method, of providing a meansfor an operator to select a desired roll orientation that is to beautomatically maintained at a distal tip of a robotic endoscope.

These and additional objects are accomplished by the various aspects ofthe present invention, wherein briefly stated, one aspect is a computerimplemented method for controlling operator commanded movement of adistal tip of a robotic endoscope while maintaining a roll orientationat the tip, the method comprising: receiving a control input from anoperator manipulatable input control device; determining a currentcommanded state of the tip of the robotic endoscope from the controlinput, wherein the current commanded state includes a current commandedroll position and velocity; modifying the current commanded state byconstraining the current commanded roll position and velocity to be amodified current commanded roll position and velocity according to aroll angular adjustment indicated by a prior process period commandedstate of the tip and a setpoint indicative of the roll orientation to bemaintained at the tip; and commanding the tip of the robotic endoscopeto be driven to the modified current commanded state.

Another aspect is a medical robotic system comprising: a roboticendoscope having an elongate body including one or more bendablesegments and a distal tip; a manipulator having one or more drivablejoints for manipulating the robotic endoscope in corresponding degreesof freedom movement; an operator manipulatable input control device; anda processor configured to receive a control input from the operatormanipulatable input control device, determine a current commanded stateof the tip of the robotic endoscope from the control input wherein thecurrent commanded state includes a current commanded roll position andvelocity, modify the current commanded state by constraining the currentcommanded roll position and velocity to be a modified current commandedroll position and velocity according to a roll angular adjustmentindicated by a prior process period commanded state of the tip and asetpoint indicative of the roll orientation to be maintained at the tip,and commanding the tip of the robotic endoscope to be driven to themodified current commanded state.

Additional objects, features and advantages of the various aspects ofthe present invention will become apparent from the followingdescription of its preferred embodiment, which description should betaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a medical robotic system utilizing aspects of thepresent invention.

FIG. 2 illustrates a schematic diagram of a robotic endoscope of themedical robotic system utilizing aspects of the present invention.

FIG. 3 illustrates a tip of a robotic endoscope being oriented indifferent directions without roll orientation compensation.

FIG. 4 illustrates a tip of a robotic endoscope being oriented indifferent directions with roll orientation compensation according toaspects of the present invention.

FIG. 5 illustrates a block diagram of components of a control processorfor operator selection of a setpoint and control of a tip of the roboticendoscope, as included in the medical robotic system utilizing aspectsof the present invention.

FIG. 6 illustrates a display screen displaying an image captured by acamera at a distal tip of a robotic endoscope and a graphicalrepresentation of current roll angle and roll setpoint indicators asviewed on a display of the medical robotic system utilizing aspects ofthe present invention.

FIG. 7 illustrates a flow diagram of a computer implemented method forcontrolling operator commanded movement of a distal tip of a roboticendoscope while maintaining a roll orientation at the tip, utilizingaspects of the present invention.

FIG. 8 illustrates a fixed reference frame and a reference frameassociated with the distal tip of the robotic endoscope that moveswithin the fixed reference frame as used in the medical robotic systemutilizing aspects of the present invention.

FIG. 9 illustrates a flow diagram of a computer implemented method fordetermining a roll angular adjustment in the medical robotic systemutilizing aspects of the present invention.

FIG. 10 illustrates a graphical depiction of determining a roll angularadjustment as used in the medical robotic system utilizing aspects ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates, as an example, a medical robotic system 100including a robotic endoscope 110, a plurality of fiber optic cables 120inserted in the endoscope 110, a control processor 130 with memory 135,an actuating system 140, an image processor 150, a display screen 160,and input control devices 171, 172. The control processor 130 and imageprocessor 150 (as well as any other processors or controllers describedherein) may each be implemented as hardware, firmware, software or acombination thereof, which interact with or are implemented in one ormore computers. The display screen 160 preferably comprises left andright eye screens incorporated in a computer monitor so as to be capableof displaying three-dimensional images to an operator of the system 100.However, for cost considerations, it may be a standard computer monitorcapable of only displaying two-dimensional images. Although only onedisplay screen is shown, additional display screens may be provided sothat, for example, an assistant may view a display screen that has beenpositioned near the assistant while the surgeon is viewing the displayscreen 160. The input control device 171 is preferably a six-dimensional(6-D) joystick (either rate or position type) capable of commanding atleast six degrees-of-freedom (DOF) movement (e.g., three translationaland three orientational). The input control device 172, on the otherhand, may be a conventional computer input device such as a computermouse or keyboard.

The robotic endoscope 110 has a flexible elongate body 114 withpreferably at least two controllably bendable segments. It has at leastone controllably bendable segment that results in a steerable tip 112 atits distal end 111. It also has an actuating system 140 coupled to itsproximal end 115 for actuating movement of the endoscope 110 and itscontrollably bendable segments. Control cables or other conventionalcontrol means (not shown) extend from the actuating system 140 to the atleast one controllably bendable segment of the steerable tip 112 so thatthe tip 112 may be controllably bent or turned, as shown for example bydotted line versions of the bent tip 112. Other cables or otherconventional control means (not shown) may also extend in this exampleto other controllably bendable segments so that they may be controllablybent. Passive bendable segments may also be included in the roboticendoscope as well as bendable segments that are constrained in somefashion to move with other bendable segments.

Referring to FIG. 2, the actuating system 140 includes an endoscopemanipulator 231 and one or more bend actuators 232. The endoscopemanipulator 231 serves to actuate the robotic endoscope 110 in twodegrees of freedom. One degree of freedom is an insertion/retractionmovement (as illustrated by the dotted line, two-headed arrow labeled“I/O”) implemented with a prismatic joint that moves the proximal end115 of the robotic endoscope 110 forward and backward. The other degreeof freedom is a proximal roll rotation (as illustrated by the dottedline, two-headed arrow labeled “φ”) implemented with a rotary joint thatrotates the robotic endoscope 110 about its insertion/retractiondirection. The bend actuators 232 actuate bending segments 201-203 ofthe robotic endoscope 110 so they are each bendable in respective pitchrotations (as illustrated by the dotted line, two-headed arcs α₁α₃) andyaw rotations (as illustrated by the dotted line, two-headed arcsβ₁-β₃). In addition to the bendable segments, a first link 211 of therobotic endoscope 110 is coupled at its proximal end to the endoscopemanipulator 231 and at its distal end to rest of the body 114 so that asthe endoscope manipulator 231 causes the link 211 to move in either theI/O direction or roll rotation (φ), then the rest of the body 114 (andin particular, all of the bendable segments 201-203 and coupling links212-215 that couple with the bendable segments 201-203) move in unisonwith the first link 211.

One or more of the fiber optic cables 120 (shown in FIG. 1) arepreferably configured with bend or shape sensors such as Fiber BraggGratings (or other strain sensors such as those employing Rayleighscattering) so that light passing through the fiber optic cable isprocessed by the control processor 130 (or a separate positionprocessor) to determine a current position and shape of the endoscope110 including the orientation of its distal tip 112. In addition to thefiber optic cables 120 extending through the endoscope 110, one or moreadditional fiber optic cables (not shown) configured with strain sensorsmay be attached to the endoscope 110 so as to provide positioninformation of the endoscope 110 at the attachment point. Additionaldetails on the determination of the endoscope's position and bendingusing Fiber Bragg Gratings may be found, for examples, in U.S.2007/0156019 A1 entitled “Robotic Surgery System Including PositionSensors Using Fiber Bragg Gratings”; U.S. 2008/0212082 A1 entitled“Fiber Optic Position and/or Shape Sensing Based on Rayleigh Scatter”;U.S. 2008/0218770 A1 entitled “Robotic Surgical Instrument and Methodsusing Bragg Fiber Sensors”; and U.S. application Ser. No. 12/164,829entitled “Fiber Optic Shape Sensor; each of which is incorporated hereinby reference. Additional details for a conventional steerable endoscopemay be found for example in U.S. Pat. No. 6,869,396 B2 entitled“Steerable Endoscope and Improved Method of Insertion”, which isincorporated herein by reference. Although fiber optic sensors are thepreferred means for bend or shape sensing, other sensors may also beused in practicing the present invention, such as electro-magneticsensors, potentiometers, etc.

A stereoscopic or monoscopic camera is provided at the distal tip 112 ofthe endoscope 110 for capturing images that are transmitted to andprocessed by the image processor 150 and displayed on the display screen160 in a conventional manner for endoscopes. One of the fiber opticcables 120 may be coupled at its proximal end to a light source (notshown) for illumination purposes at the distal tip 112. A distal tipreference frame 200 is defined at the distal tip 112 by a depth axisZ_(TIP), a horizontal axis X_(TIP) and a vertical axis Y_(TIP) of a viewof the camera as it looks away from the distal tip 112.

As simplistically shown in FIG. 3, when the distal tip 112 is bent inone direction 301 or another direction 302, its horizontal orientation300 (as defined by the X_(TIP)-Z_(TIP) plane) may change with respect toits surroundings. As previously explained, such changes in horizontalorientation relative to the surroundings may disorient the operator asthe operator views the area from images that are captured by the distaltip camera and displayed on the display screen 160. To prevent suchdisorientation, ideally, as shown in FIG. 4, when the distal tip 112 isbent in any direction, its horizontal orientation 300 remains the samewith respect to its surroundings. For example, it may be desired thatthe horizontal orientation 300 is always perpendicular to the force ofgravity.

FIG. 5 illustrates, as an example, a block diagram of components of thecontrol processor 130 that allow an operator to select or change asetpoint, which indicates a desired roll orientation of a camera viewcaptured at the distal tip 112 of the robotic endoscope 110, and tocommand movement of the distal tip 112 while the system automaticallymaintains the desired roll orientation at the distal tip 112. Theoperator interacts with a setpoint processor 132 using an appropriateinput device such as the input control device 172 to select or changethe setpoint and commands movement of the distal tip 112 of the roboticendoscope 110 using the input control device 171.

An initial or default setpoint may be established with or withoutoperator intervention using gravity to generate a reference. In thiscase, a reference vector Y_(SP) indicating the setpoint may be definedso that it points in an opposite direction from the gravity vector. Thesetpoint may subsequently be changed (or initially established if adefault setpoint has not been defined) by the operator interacting withthe setpoint processor 132. For example, the operator may select thesetpoint so that it corresponds to a current roll orientation of the tip112 by depressing a select button on one of the input control devices171, 172, or using a voice command recognized for such purpose by avoice recognition system (not shown), or using any other well knowninteractive means. In this case, the setpoint processor 132 defines thereference vector Y_(SP) indicating the setpoint so that it points in thesame direction as the Y_(TIP) axis of the tip's camera view at the timeof such operator selection input. The tip reference frame (X_(TIP),Y_(TIP), Z_(TIP)) is determined in a conventional manner from a currenttip position and orientation generated by forward kinematics processor136 from sensed joint positions 138 of the actuating unit 140.

As another example, the operator may establish the setpoint byinteracting with a Graphical User Interface (GUI). As illustrated inFIG. 6, the setpoint processor 132 may be implemented to include the GUIwhich includes the display screen 160 upon which a graphics image 600 isdisplayed adjacent an image 350 captured by the distal tip camera. Thegraphics image 600 includes a current roll angle indicator 601 and agraphically rotatable roll setpoint indicator 602. The GUI allows aninput control device such as the input control device 172 to interactwith the rotatable roll setpoint indicator 602 of the graphics image600. For example, in response to movement of the input control device172 by its operator, the roll setpoint indicator 602 may be rotated to adifferent angle, as shown in FIG. 6, from the current roll angleindicator 601. Meanwhile, as the operator causes the roll setpointindicator 602 to rotate, the input handler 131 causes the distal tiproll angle (φ_(TIP)) and the current roll angle indicator 601 to trackthe movement so that when the distal tip roll angle matches the angleindicated by the rotatable roll setpoint indicator 602, the selectableroll setpoint indicator 602 disappears on the display screen 160 and thecurrent roll angle indicator 601 remains.

Referring back to FIG. 5, the operator commands movement of the distaltip 112 of the robotic endoscope 110 by moving the input control device171. If the input control device 171 is a position type device, itsmovement defines 6 DOF of translational and orientational positions. Inthis case, 6 DOF of translational and orientational velocities may becalculated in a conventional manner by dividing corresponding changes inposition between successive process periods by the duration of a processperiod. On the other hand, if the input control device 171 is a ratetype device, its movement defines 6 DOF of translational andorientational velocities. In this latter case, 6 DOF of translationaland orientational positions may each be calculated in a conventionalmanner by adding the product of a corresponding velocity and theduration of the process period to a position value calculated (orinitially set) for the immediately prior process cycle. In either case,the additional velocity or position calculations are performed by aninput processor that is considered, for the purposes of simplifying thedescription, part of the input control device 171.

The input handler processor 131 processes the output of the inputcontrol device 171 to generate a current commanded state of the distaltip 112 relative to a fixed Cartesian X, Y, Z reference frame (e.g.,fixed frame 800 of FIG. 8) and modifies the current commanded stateusing information of the setpoint provided by the setpoint processor 132to generate a modified current commanded state of the distal tip 112. Adetailed description of the processing performed by the input handlerprocessor 131 is described herein in reference to FIGS. 7-10. Themodified current commanded state takes into account both the operatorcommanded movement of the distal tip 112 and the requirement to maintainthe roll orientation at the distal tip 112 (i.e., maintain the angle ofthe horizon defined by the X_(TIP)-Z_(TIP) plane of the distal tipcamera view relative to a reference vector Y_(SP) associated with thesetpoint).

An inverse kinematics processor 134 receives the commanded state of thedistal tip 112 from the input handler processor 131 and transforms it tocorresponding joint commands for driving the endoscope manipulator 231and bend actuators 232. The transformation is performed by applying thecommanded state in a conventional manner to inverse kinematics of thecombined serial kinematic chain composed of the endoscope manipulator231 and the robotic endoscope 110. A joint control processor 135includes a joint control system for each joint being actuated andcontrolled by the endoscope manipulator 231 and bend actuators 232. Theoutput of the inverse kinematics processor 134 is provided to the jointcontrol processor 135 which controls operation of the actuating unit 140through actuating commands 137 so that controllable joints of theendoscope manipulator 231 and controllably bendable segments of therobotic endoscope 110 are driven to proper positions so as to effect thecommanded state of the distal tip 112 of the robotic endoscope 110.

FIG. 7 illustrates, as an example, a flow diagram of a method performedin the input handler processor 131 for controlling operator commandedmovement of the distal tip 112 of the robotic endoscope 110 whilemaintaining a roll orientation at the tip 112 corresponding to thesetpoint. In 701, the method receives an operator input from the inputcontrol device 171. In 702, the method transforms the operator input toa current commanded state of the distal tip 112 of the endoscope 110 ina conventional manner by applying, for example, the 6 DOF translationaland orientational positions and velocities received from the inputcontrol device 171 to known transforms to generate the current commandedstate in corresponding 6 DOF translational and orientational positionsand velocities of the tip 112. The term “current command” as used hereinrefers to a command issued for the current process cycle or period(e.g., time “t”) and the term “prior process command” as used hereinrefers to a command that had been issued in a prior process cycle orperiod (e.g., time “t−1”).

In 703, the method determines a roll angular adjustment (Δφ_(TIPA))using information of an immediately prior process commanded state of thetip 112 and the setpoint. The roll angular adjustment represents achange in roll angle about the Z_(TIP) axis that is required to maintainthe horizontal X_(TIP) axis of the view captured by a camera at thedistal tip 112 with the roll orientation indicated by the setpoint. Aspreviously explained in reference to FIG. 5, the setpoint may beoperator selected or it may be automatically established using, forexample, a gravity sensing mechanism, such as described in previouslyincorporated by reference U.S. Pat. No. 7,134,992, in which case, theroll orientation is preferably a horizontal line perpendicular to thedownward pointing gravity vector.

An example of a method for performing 703 is illustrated in FIG. 9,wherein in 901, the reference vector Y_(SP) which is indicative of thesetpoint and whose generation was previously described in reference toFIG. 5, is received from the setpoint processor 132. As the distal tip112 moves and orients in various directions, its distal tip referenceframe 200, which has orthogonal axes X_(TIP), Y_(TIP) and Z_(TIP) asdefined in reference to FIG. 2, moves accordingly. For example, as shownin FIG. 8, a reference vector Y_(SP) is shown as being established bythe operator when the tip 112 was previously at a tip reference frameposition and orientation indicated as 200′ in a fixed reference frame800. Subsequent movement of the tip 112 resulted in the tip referenceframe position and orientation moving as indicated by tip referenceframe 200 in the fixed reference frame 800. In 902, the reference vectorY_(SP) is then projected onto a plane including the Y_(TIP) axis and theZ_(TIP) axis of the tip reference frame, such as shown in FIG. 10. Thetip reference frame 200 may be provided in this case from a priorprocess cycle commanded state of the tip 112 (such as the immediatelyprior process period as shown in FIG. 5) or it may be provided frominformation received from the forward kinematics processor 136 thatindicates a sensed state of the tip 112. In 903, the roll angleadjustment (Δφ_(TIPA)) is then determined as the angle between thereference vector Y_(SP) and its projection Y′_(SP) on theY_(TIP)-Z_(TIP) plane, as also shown in FIG. 10.

In 704, a determination is made whether the roll angular adjustmentdetermined in 703 is less than a threshold value. If the roll angularadjustment is less than the threshold value (i.e., the roll angularadjustment is relatively small), then the method proceeds to 705,otherwise, it proceeds to 707. The threshold value may be set to somefixed value such as 5 degrees or some other angle that results in achange in the roll orientation of the distal camera view as seen in thecaptured image 350 on the display screen 160 that an operator would findimperceptible or at least would not be disorienting to the operator. Tosatisfy operator preferences, the GUI described in reference to FIG. 6may also be modified by adding some means that allows the operator tospecify and/or adjust the threshold value.

In 705, since the roll angular adjustment has been determined to be lessthan the threshold value, then the method modifies the current commandedroll velocity ({dot over (φ)}_(TIPC)) to zero and in 706, it modifies,if necessary, the current commanded roll position, i.e., φ_(TIPC)(t), toits immediately prior process cycle commanded roll position, i.e.,φ_(TIPC)(t−1), so that the current roll orientation at the distal tip112 would be maintained.

On the other hand, in 707, when the roll angular adjustment has beendetermined to be equal to or more than the threshold value, then themethod modifies the current commanded roll angular velocity ({dot over(φ)}_(TIPC)) to a value that is either a function of the roll angularadjustment or to a constant value, depending upon the selectedembodiment of the present invention, and in 708, it modifies the currentcommanded roll position, i.e., φ_(TIPC)(t), so as to be consistent withthe modified current commanded roll velocity ({dot over (φ)}_(TIPC)),using for example, the following equation:

φ_(TIPC)(t)={dot over (φ)}_(TIPC)(t)·ΔT+φ _(TIPC)(t−1)  (1)

where “{dot over (φ)}_(TIPC)(t)” is the modified current commanded rollvelocity, “AT” is the duration of the process cycle or period, and“φ_(TIPC)(t−1)” is an immediately prior process period commanded rollposition (previously stored in and currently read from storage elementor memory 133 in FIG. 5).

Either or both the function and the constant used in 707 may possibly bescaled proportionally with the magnitude of the total commanded tipvelocity in order to avoid large and/or abrupt changes that may surprisethe operator. In one example of such a function, the function may beconstructed so that the current commanded roll velocity ({dot over(φ)}_(TIPC)) gets larger as the roll angular adjustment gets larger(with some maximum value). When the current commanded roll velocity({dot over (φ)}_(TIPC)) is set to a constant, such a limiting of themagnitude of the current commanded roll velocity may lengthen the amountof time required to arrive at the current commanded roll position, butwill prevent large, potentially dangerous tip velocity commands fromoccurring.

In 709, the method transforms the operator input to a modified currentcommanded state of the endoscope tip 112 in a conventional manner suchas in 702, except this time the modified current commanded roll velocityis constrained to be equal to the value determined in either 705 or 707and the modified current commanded roll position is constrained to beequal to the value determined in either 706 or 708, depending upon theresult of 704. Alternatively, the modified current command state of theendoscope tip 112 may be simply formed by merely replacing the currentcommanded roll position in the current commanded state with the modifiedcurrent roll position and replacing the current commanded roll velocityin the current commanded state with the modified current commanded rollposition. In 710, the modified commanded state of the distal tip 112 isthen provided to the inverse kinematics processor 134 as previouslydescribed in reference to FIG. 5.

Although the various aspects of the present invention have beendescribed with respect to one or more preferred embodiments, it will beunderstood that the invention is entitled to full protection within thefull scope of the appended claims.

1. A method for controlling operator commanded movement of a distal tipof a robotic endoscope while maintaining a roll orientation at the tip,the method comprising: receiving a control input from an operatormanipulatable input control device; determining a current commandedstate of the tip of the robotic endoscope from the control input,wherein the commanded state includes a current commanded roll positionand velocity; modifying the current commanded state by constraining thecurrent commanded roll position and velocity to be a modified currentcommanded roll position and velocity according to a roll angularadjustment indicated by a prior process period commanded state of thetip and a setpoint indicative of the roll orientation to be maintainedat the tip; and commanding the tip of the robotic endoscope to be drivento the modified current commanded state.
 2. The method according toclaim 1, wherein a tip reference frame is defined at the tip of theendoscope so as to have a Z_(TIP) axis indicative of a depth directionof a view captured at the tip, a X_(TIP) axis indicative of a horizontaldirection of the view, and a Y_(TIP) axis indicative a verticaldirection of the view, the method further comprising: receiving areference vector indicative of the setpoint; projecting the referencevector onto a plane containing the Y_(TIP) axis and the Z_(TIP) axis;and determining the roll angular adjustment as an angle between thereference vector and the projected reference vector.
 3. The methodaccording to claim 1, where the current commanded roll velocity ismodified by setting it to zero and the commanded roll position ismodified by setting it to the prior process period commanded rollposition as long as the roll angular adjustment is less than a thresholdvalue.
 4. The method according to claim 1, wherein the current commandedroll velocity is modified by setting it to a fixed value and thecommanded roll position is adjusted to a value consistent with themodified current commanded roll velocity whenever the roll angularadjustment is greater than a threshold value.
 5. The method according toclaim 1, wherein the current commanded roll velocity is modified so asto be a function of the roll angular adjustment and the currentcommanded roll position is adjusted to a value consistent with themodified current commanded roll velocity whenever the roll angularadjustment is greater than a threshold value.
 6. The method according toclaim 1, wherein the setpoint is established so as to be orthogonal togravity.
 7. The method according to claim 1, further comprising:receiving an indication of the setpoint from an operator manipulatedinput device.
 8. The method according to claim 7, wherein the setpointis established by a roll orientation at the tip at the time that theindication of the setpoint is received from the operator.
 9. The methodaccording to claim 7, further comprising: displaying a graphicalrepresentation of the setpoint on a display screen viewable by theoperator; receiving an input from the operator manipulated input device;adjusting an orientation of the graphical representation of the setpointon the display screen according to the received input; and determiningthe setpoint from the adjusted orientation of the graphicalrepresentation of the setpoint.
 10. The method according to claim 1,wherein the commanding of the tip of the robotic endoscope to be drivento the modified current commanded state comprises: determining acombination of states for one or more joints of a manipulator thatmanipulates the robotic endoscope in corresponding degrees of freedommovement and bending angles for one or more bending segments of therobotic endoscope to bend a body of the robotic endoscope so as toachieve the modified current commanded state of the tip of the roboticendoscope; and commanding the one or more joints of the manipulator tobe driven to the determined joint states and the one or more bendingsegments of the robotic endoscope to be driven to the determined bendingangles.
 11. The method according to claim 10, wherein the one or morejoints of the manipulator includes a prismatic joint for moving aproximal end of the robotic endoscope forward and backward along alinear path and a rotary joint for rotating the proximal end of therobotic endoscope about the linear path.
 12. The method according toclaim 10, wherein the determining of the current commanded state of thetip of the robotic endoscope from the control input comprises:determining translational and angular tip states from the control inputand stored information of control inputs for one or more prior processperiods.
 13. The method according to claim 10, wherein the determiningof the current commanded state of the tip of the robotic endoscope fromthe control input comprises: transforming the control input to a desiredstate of the tip of the robotic endoscope relative to a fixed Cartesianreference frame.
 14. The method according to claim 13, wherein thedetermining of the states of the one or more joints of the manipulatorand bending angles for the one or more bending segments of the roboticendoscope comprises: applying the modified current commanded state toinverse kinematics of the combined serial kinematic chain composed ofthe manipulator and the robotic endoscope.
 15. A medical robotic systemcomprising: a robotic endoscope having an elongate body including one ormore bendable segments and a distal tip; a manipulator having one ormore drivable joints for manipulating the robotic endoscope incorresponding degrees of freedom movement; an operator manipulatableinput control device; and a processor configured to receive a controlinput from the operator manipulatable input control device, determine acurrent commanded state of the tip of the robotic endoscope from thecontrol input wherein the current commanded state includes a commandedroll position and velocity, modify the current commanded state byconstraining the current commanded roll position and velocity to be amodified current commanded roll position and velocity according to aroll angular adjustment indicated by a prior process period commandedstate of the tip and a setpoint indicative of the roll orientation to bemaintained at the tip, and command the tip of the robotic endoscope tobe driven to the modified current commanded state.
 16. The medicalrobotic system according to claim 15, wherein a tip reference frame isdefined at the tip of the endoscope so as to have a Z_(TIP) axisindicative of a depth direction of a view captured at the tip, a X_(TIP)axis indicative of a horizontal direction of the view, and a Y_(TIP)axis indicative a vertical direction of the view; and wherein theprocessor is further configured to receive a reference vector indicativeof the setpoint, project the reference vector onto a plane containingthe Y_(TIP) axis and the Z_(TIP) axis, and determine the roll angularadjustment as an angle between the reference vector and the projectedreference vector.
 17. The medical robotic system according to claim 15,where the processor is configured to modify the current commanded rollvelocity by setting it to zero and modify the current commanded rollposition by setting it to the prior process period commanded rollposition as long as the roll angular adjustment is less than a thresholdvalue.
 18. The medical robotic system according to claim 15, wherein theprocessor is configured to modify the current commanded roll velocity bysetting it to a fixed value and adjust the current commanded rollposition to a value consistent with the modified current commanded rollvelocity whenever the roll angular adjustment is greater than athreshold value.
 19. The medical robotic system according to claim 15,wherein the processor is configured to modify the current commanded rollvelocity so as to be a function of the roll angular adjustment andadjust the commanded roll position to a value consistent with themodified current commanded roll velocity whenever the roll angularadjustment is greater than a threshold value.
 20. The medical roboticsystem according to claim 15, wherein the setpoint has been establishedso as to be orthogonal to gravity.
 21. The medical robotic systemaccording to claim 15, wherein the processor is configured to receive anindication of the setpoint from an operator manipulated input device.22. The medical robotic system according to claim 21, wherein theprocessor is configured to establish the setpoint by a roll orientationat the tip at the time that the indication of the setpoint is receivedfrom the operator.
 23. The medical robotic system according to claim 21,further comprising: a display screen; and an operator manipulatableinput device; wherein the processor is configured to display a graphicalrepresentation of the roll setpoint on the display screen, receive aninput from the operator manipulatable input device, adjust anorientation of the graphical representation of the roll setpoint on thedisplay screen according to the received input, and determine the rollsetpoint from the adjusted orientation of the graphical representationof the roll setpoint.
 24. The medical robotic system according to claim15, wherein the processor is configured to command the tip of therobotic endoscope to be driven to the modified current commanded stateby determining a combination of states for the one or more joints of themanipulator and bending angles for the one or more bendable segments ofthe elongate body so as to achieve the modified current commanded stateof the tip of the robotic endoscope; and commanding the one or morejoints of the manipulator to be driven to the determined joint statesand the one or more bendable segments of the robotic endoscope to bedriven to the determined bending angles.
 25. The medical robotic systemaccording to claim 24, wherein the one or more joints of the manipulatorincludes a prismatic joint for moving a proximal end of the roboticendoscope forward and backward along a linear path and a rotary jointfor rotating the proximal end of the robotic endoscope about the linearpath.
 26. The medical robotic system according to claim 20, wherein theprocessor is configured to determine the current commanded state of thetip of the robotic endoscope from the control input by determiningtranslational and angular tip states from the control input and storedinformation of control inputs for one or more prior process periods. 27.The medical robotic system according to claim 24, wherein the processoris configured to determine the commanded state of the tip of the roboticendoscope from the control input by transforming the control input to adesired state of the tip of the robotic endoscope relative to a fixedCartesian reference frame.
 28. The medical robotic system according toclaim 27, wherein the processor is configured to determine the states ofthe one or more joints of the manipulator and the bending angles for theone or more bendable segments of the robotic endoscope by applying themodified current commanded state to inverse kinematics of the combinedserial kinematic chain composed of the manipulator and the roboticendoscope.